One danger in describing "Constellations" -- and there are more than a few -- is that Nick Payne's time-traveling, two-character, 70-minute invention will sound like a technical gimmick. Another peril would be to let his way of repeating short scenes with different emphases suggest just an acting exercise. Or worse, upon learning that the action takes place in "The Multiverse" of the "Past, Present and Future" and that a character is a quantum cosmologist, one could be excused for dreading a physics lesson.

In fact, with actors less compelling and unpretentiously appealing as Jake Gyllenhaal and Ruth Wilson, it's likely that this deeply moving and unpredictable romance would never have made it to Broadway at all. But here they are, making their dazzling Broadway debuts as characters who, despite the br...